In an ancillary study to the Coronary Drug Project (CDP), the basic aim is to assess the ability of several non-invasive objective measurements of cardiovascular functional status to predict prognosis (particularly risk of mortality, including sudden death) in middle-aged men with a history of myocardial infarction. Eight CDP centers - in Baltimore, Chicago and Minneapolis-St. Paul, with about 1,000 surviving patients - are cooperating in this effort, in accordance with a uniform common protocol. Key non-invasive techniques are Holter Avionics tape recording of ECG during usual daily activity, ultra low- frequency ballistocardiography (Bcg), apex cardiography, impedance plethysmography to assess circulation in the lower extremities. Bcgs are tape recorded and evaluated by computer. For all other indices, intra-observer and inter-observer variability and reproducibility are assessed. Extensive data on multiple variables will be accrued from CDP central files. Patients will be followed for five years to assess mortality, by cause. Particular attention will be given to modern multivariate methods (e.g., 40 variables) of statistical analysis, in order to evaluate the key question of the independent predictive power of the indices.